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Tutorial 3&4

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by

Wael El Basel

on 26 January 2015

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Transcript of Tutorial 3&4

Exercise (3)
Rules used in this exercise
Logging Tools
Permeability tools
Spontaneous Potential log
Natural electric potential that develops as a result of ion movement between solutions of different salinities where CL- ions separate from NA+ ions and attracted by the shales measured by milli-volts (mv)
Origin of SP
SP currents are caused by electro motive forces in the formation represented in
Limitations
1) Oil base-mud
SP
GR
Porosity tools
SONIC
DENSITY
NEUTRON
Fluid type
RESISTIVITY
At permeable formation , SP is -ve ( Rw<Rmf)
At im-permeable formation , SP is +ve (Rw>Rmf)
+
shale base-line
-
sand base-line
SP
SSP : difference between sand base-line and shale base-line
2) Dry hole
3) Cased hole
due to the absence / presence of non conductive materials that provide electrical continuity between the fixed and moving electrode
Electrochemical component
Electrokinetic component
occurs due to movement of NA+CL- from higher salinity to a lower one
occurs due to the flow of mu filtrate through the mud cake
SSP= -K log (Rmf eq/Rw eq)
K = 61+0.133 (T)
Rmf2 = Rmf1 X (T1+6.77 / T2+6.77)
V sh = 1 - ( sp/ssp )
T --> B.H.T
Rmf2 --> B.H
Rmf1 --> Surface Temp.
V sh
0-10 sand
10-35 shaly sand
35<X shale
Number (1)
Fill in the blanks in the following table :

Number (2)
For a drilled well and shown in the next figure:
Determine formation water resistivity, Rw and Lithofacies properties of the logged section.
Is there producing zone(s)?

Rmf= 0.64 @78 F
BHT= 190 F @10,500 ft
Mean Surface Temp.= 80 F
1) Convert Rmf from Surface to BHT
2) Get Rmf eq chart
3) Get K
4) Get Rw eq from SSP rule
5) Get Rw from chart
6) Calculate V sh
Number (3)
Determine formation water resistivity, Rw from the SP for the two zones at 8990 and 9200 shown in the next figure.
If the Rw's differ, explain the reason why ?

Rmf= 0.64@ 90 F
BHT = 219 F
The water resistivity at 9200 decreases as the temperature increases therefore more salt can be dissolved in the water which indicates the increase in conductivity and reduction in resistivity
Number (4)
Tutorial 3 & 4
Gamma Ray
It's a continuous recording of the natural radiations emitted from the formation measured in (API) , most of those radiations are present in the radio active materials ( thorium - potassium - uranium ) found in clay and shales while sandstones and limestones contain very low radio active isotopes.
GR works through cased & dry holes , though the steel pipe absorb some of the gamma ray which decreases its intensity but enough GR reach the tool at the end.
Rules used in this exercise
IGR =
GR - GR max
GR min - GR max
Vsh= 0.083(2 - 1)
3.7 x IGR
POST TERTIARY , CLASTIC ROCKS , LATE QUATERNARY
Vsh= 0.33(2 -1)
2 x IGR
PRE-TERTIARY , CRETACEOUS , CARBONATE
Number (1)
Determine the Vsh for the selected zones in the CARBONATE sequence shown in example well B , figure H-2-3
GR min
GR
max
Number 2
In figure H-2-4 calculate Vsh fro total counts (GR) .Assuming formations are cretaceous except formations A & B are late quaternary
Given that :

minimum CTS 12
maximum CTS 120
GR max
GR min
K
Ur
Th
A=75
B=75


C=15
D=15
E=17
F=110
G=22
Number 3
Draw a GR&SP for a sequence of thick formations which are from the top to bottom , SHALE , PERMEABLE LAYER, SHALE, IMPERMEABLE LAYER, SHALE, PERMEABLE LIMESTONE & RADIO ACTIVE SAND.
Number 4
Figure H-2-6 is a composite log of GR and NGS zone. Determine if Zone A is radio active and explain .
Natural GR spectometer
THANK YOU
Wael EL Basel
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